1. Field of the Invention
The present invention generally relates to the field of layout patterns in semiconductor devices, and more particularly to a method for forming a layout pattern in non-planar semiconductor devices.
2. Description of the Prior Art
Integrated circuits (IC) are made of devices and interconnections, which are formed through patterned features in different layers. During the fabrication process of ICs, the photolithography is an essential technique. The photolithography is used to form designed patterns, such as implantation patterns or layout patterns, on at least a photomask, and then to precisely transfer such patterns to a photoresist layer through exposure and development steps. Finally, by performing several semiconductor processes such as etching processes, ion implantations, depositions and so forth, complicated and sophisticated IC structures can be obtained.
With the continuous miniaturization of semiconductor devices and the remarkable advance in fabrication techniques of semiconductor devices, the conventional lithography process meets its limitation due to printability and manufacturability problems. To meet the requirements of device design rules which continue to push the resolution limits of existing processes and tooling, a double patterning technique (DPT) has been developed and taken as one of the most promising lithography technologies for 32 nanometer (nm) node and 22 nm node patterning, since it can increase the half-pitch resolution up to twice higher by using current infrastructures. Besides, three-dimensional or non-planar transistor technology, such as the fin field effect transistor (FinFET) technology, has also been developed to replace planar MOS transistors. Generally, patterned structures in a FinFET, such as fin structures, can be obtained by sidewall image transfer (SIT).
Although the above-mentioned technologies, i.e. DPT and 3-D transistor technology, have been widely adopted by semiconductor manufacturers and successively overcome major drawbacks in the fabricating process, there are still some problems needed to be solved. For example, in order to prevent or overcome optical problems, such as optical proximity effect, in photolithography processes and polishing problems, such as dishing phenomenon, in planarization processes, dummy patterns are often added to layout patterns of semiconductor devices through proper computer simulation at the beginning of the fabrication process. However, how to effectively distribute different dummy patterns over individual photomasks is still a major topic for study in the semiconductor field.